In the meanwhile, the enhanced H abstraction reaction [34, 35] of the increasing H atoms and ions took away a certain number of the bonded

H from the hydrides at grain boundaries, and more oxygen impurities could incorporate the dangling bonds at grain boundaries, giving rise to the decrease of the integrated intensity of the MSM and the increase of C O as shown in Figure  5b. Further increasing R H from 98.6% to 99.2% led to a declining growth rate due to the further decreasing density of the SiH x radicals. At the same time, the P V of the growing film was further enhanced SCH727965 mouse (see Figure  2b) because of the ion bombardment effect of the excessive H species. Pictilisib molecular weight However, in this R H range, 98.6% to 99.2%, the MLN8237 in vitro hydrogen-induced annealing effect [36] gradually became dominant over the effect of the ion bombardment-induced amorphization. The excessive H species presenting on the growing surface of the film could penetrate into the subsurface and rearrange the Si-Si network

structure. These H atoms and ions saturated the present dangling bonds at the interface between the amorphous and crystalline regions and formed molecular hydrogen through the reaction of adsorbed hydrogen with clustered hydrogen in the subsurface, which was less mobile than the atomic hydrogen. Further H insertion reaction with the a-Si:H matrix destructed and perturbed the strained Si-Si bonds, and the subsequent structural relaxation of the Si-Si bonds resulted in the transformation of the film’s structure from amorphous

Thymidylate synthase to nanocrystalline. Therefore, as a general result, excessive hydrogen presenting in the plasma could lead to a greater probability of crystallization, supported by the observation of X C in Figure  1c. The slight enhancement of the grain size d from 5.5 to 6.1 nm as seen in Figure  1a without any remarkable change can be attributed to the suppression of the growth by the excessive H ion implantation on the nucleation site, as well as the depletion of the SiH x radical by the hydrogen flux. On the other hand, the results of the increasing integrated intensity of the MSM and the decreasing C O as shown in Figure  5b in this R H range illustrate that those H atoms and ions penetrating into the subsurface could saturate the dangling bonds along the grain boundaries, and more hydrides were formed to effectively avoid the post-oxidation effect by preventing the oxygen impurities from incorporating the dangling bonds in the grain boundaries. Hence, compact-structure and well-passivated grain boundaries are less susceptible to oxygen impurities. Our previous work of applying an extra negative bias on the substrate [37] offers an effective way to lower the defect density and the oxygen impurities inside nc-Si:H films.